Not sure, but it's an event pokemon from what I can tell. (Actually, looks like its wi-fi event is set to start tomorrow in Japan based on what Serebii lists.) It's also 000 in the new region's pokedex for some reason too.
Roll on the day when HM's (or whatever their replacement would be) are useable by the player, so you can keep a full team at all times, rather than wasting space with slaves...